Drafting instrument



Aug. 18, 1936. H, A JR 2,051,741

DRAFT ING INS TRUMENT Filed March 25, 1935: 2 Sheets-Sheet '1 ATTORNEY Aug. 18, 1936. G. H. PARKER. JR

DRAFTING INSTRUMENT 2.Sheets -Sheet 2 Filed March 25, 1.935

ATTO R N EY Patented Aug. 18, 1936 UNITED STATES PATENT oFFioE The invention relates to drafting instruments and has for its primary object to provide a single instrument that will perform the functions required of separate instruments as employed by draftsmen in the laying out of work and that may be employed to step off lines in any direction and at the required distances apart, thus for example, cross hatching can be accomplished with clearness and cleanness and the lines uniformly spaced as well as permitting the dividing .of a circle into any number of segments and in fact the drafting work in its entirety can be effected by the single instrument without resort- .ing to the use of other independent instruments.

Another object of the invention is to provide an instrument of this character, wherein accuracy is assured in the laying out of drafting work and also measurements are determined with dispatch and the adjustment of the instrument easily had.

A further object of the invention is the provision of an instrument of this character, wherein .the construction thereof permits of the use there- ,of with a T-square and when not in use is susceptible of being folded to render the instrument compact and its storage in the least possible space.

A still further object of the invention is .the provision of an instrument of this character, whichis simple in its construction, thoroughly reliable and efficacious, easy of adjustment, assuring accuracy in the laying out of drafting work, strong, durable, and inexpensive to manufacture.

With these and other objects in view, the invention consists in the features of construction, combination and arrangement of parts as will be hereinafter more fully described, illustrated in the accompanying drawings, which disclose the preferred embodiment of the invention and pointed out in the claims hereunto appended.

In the accompanying drawings:

Figure 1 is a fragmentary plan view of a drafting board of conventional type having a T-square clamped therewith and showing the instrument constructed in accordance with the invention applied.

Figure 2 is an edge elevation.

Figure 3 is a top plan view partly broken away of one of the triangles of the instrument.

Figure 4 is an edge elevation thereof.

Figure 5 is a sectional view on the line 55 of Figure 3 looking in the direction of the arrows.

Figure 6 is a sectional View on the line 66 of Figure 4 looking in the direction of the arrows.

Figure '7 is a sectional view on the line 1- -1 of Figure 3 looking in the direction of the arrows.

Figure 8 is an edge elevation of the clamp for .one of the triangles of the instrument.

Figure 9 is an edge elevation partly in section of the clamp for the T-square.

Figure 10 is a side elevation of a rack employed in the instrument.

Similar reference characters indicate corresponding parts throughout the several views in the drawings.

Referring to the drawings in detail, A designates generally a portion of a drawing board of conventional kind used by draftsmen and B designates a T-square, this also being conventional excepting that in the blade Ii] thereof close to its end remote from the head I I of said square is a hole l2 for accommodating a removable lug l3 integral or formed with the long arm of a clamp i4, the short arm of which has fitted therewith a binding screw [5 having the winged head l6 and in this manner the T-square B can be firmly and securely fastened to the board A in working relation thereto and is susceptible of adjustment and easy removal.

The instrument constituting the present invention comprises a pair of foldable angle simu- .lating members C and D, respectively. The

member C includesa pair of arms or legs I! and 18, respectively, these susceptible of swinging movements and are pivotally joinedby a hinge IS. The arm or leg ll has formed in each side face thereof spaced apertures for the reception of pins 2| at the forked end 22 of a clamp 23 carrying a cam lever 24 so that the clamp may be securely engaged with the blade I 0 of the T-square B for the attachment of the member C with said square, the arm or leg I! being parallel with the blade l0 and disposed against one straight edge of said blade. This clamp 23 permits adjustment of the member C longitudinally of the blade and such member is susceptible of attachment to either side of the T-squa're.

The arm or leg I8 of the member C at an intermediate point thereof is provided with a notch 25 intersected by a pin 26 for easy separable engagement of a hook terminal 21 of a protractor member 28 therewith, the notch 25 being of a size to allow loose play of this member 28 when the hook terminal 21 thereof is engaged with the pin 26. Formed transversely in the arm or leg I! are the laterally converging slots 29 either of which accommodates the member 28 so that when it is engaged therein the member over-ridges the blade ill of the T-square.

The protractor member 28 at one of its arched edges is formed with teeth 30, these being set in conformity with a scale 3| borne by said member 28 and such teeth are adapted for ratchet engagement with teeth 32 provided in the slots 29 when the member is engaged with either of the same. The arm or leg ll has fitted therein a spring plunger 33 which plays against the member 28 when within either of the slots 29 to have the teeth ratchet with the teeth 32 companion thereto. In this manner the arms I1 and I3 are susceptible of adjustment with respect to each other in conformity with the scale 3| for angular disposition relative to one another for the drawing of cross hatching or angular stepped off lines. Inset in the outer edge of the arm or leg l8 next to the hinge I9 is a rack bar 34 one end being releasably engaged with a stationary keeper 35 and the other end engaged with a movable keeper 36 so that the bar 34 can be released to permit of a substitute rack having rack teeth of a changed spaced relation to each other.

The member D has the arms 31 and 38, respectively, these being similar to the arms I! and 8 but of less length than the same and this arm 38 has attached thereto the protractor member 39 corresponding to the protractor member 28. The protractor member 39 is fitted with the arm 31 identically to the fitting of the protractor member 28 with the arm These arms 31 and 38 of the member D are reversely beveled at opposite faces as at 4|] to effect the proper lay of the member D when associated with the member C as shown in Figures 1 and 2 of the drawings. The arm 31 of the member D at the hinged end 4| thereof carries a leaf spring ratch et member 42 engageable with the teeth of the ratchet bar 34 so that when the member D is placed against the arm I81 of the member C, the meeting edges of the arms l8 and 31 being in contact, the said member D can be readily shifted step by step along the arm l8 of the member C in conformity with the teeth of the ratchet bar 34 carried by the arm l8 as the member 42 ratchets over these teeth of said bar 35. Thus stepped off lines can be made by the member D any distance from each other and in any required direction. The arms l1 and N3 of the member C and the arms 31 and 38 of the member D are susceptible of angular adjustment with relation to each other through the medium of the hinges I9 and 4|, respectively.

The members C and D are readily separable from each other and foldable for the convenient carrying thereof or storage when not in use.

The instrument avoids the necessity for the use of separate tools or instruments for the laying out of drafting work as the single instrument will perform the functions of nearly all the tools or instruments used by a draftsman and accuracy is assured both in the making of angular lines and in measuring for distancing such lines and in platting.

What is claimed is:

1. A drafting instrument comprising a member having two legs which are pivotally connected at one of their ends to permit said member simulating angles, an arcuate protractor having edge teeth at the divisions of the calibrations thereon removably pivoted to one of the legs and guided through a. slot in the second leg, one of the end walls provided by the slot having teeth to engage those of the protractor and a spring influenced plunger movable through the second end wall of said slot to-contact with the protractor to bring the teeth thereof into ratchet engagement with the toothed Wall of the slot.

2. A drafting instrument comprising a member having two legs which are pivotally connected at one of their ends to permit said member simulating angles, an arcuate protractor having edge teeth at the divisions of the calibrations thereon removably pivoted to one of the legs and guided through a slot in the second leg, one of the end walls provided by the slot having teeth to engage those of the protractor, a spring infiuenced plunger movable through the second end wall of said slot to contact with the protractor to bring the teeth thereof into ratchet engagement with the toohed wall of the slot and a rack bar removably seated in the outer edge of one leg of said member, binding means for holding the rack bar on said leg and an angle simulating member slidable over said rack and leg and having a spring ratchet to engage the teeth of the rack bar.

GEORGE H. PARKER, JR. 

